Exercise is commonly known to improve physical fitness and health. The muscular and cardiovascular benefits of exercise are firmly documented. Treadmills offer aerobic and anaerobic exercise in a limited space, without regard to access to running or walking areas any greater than the space occupied by the treadmill. Typical treadmills offer slope adjustment, speed adjustment, heart rate counters, mileage meters, timers, and various other well known feedback displays and recording devices. Typical modern treadmills also offer route choices, which can take a user through simulated courses of hill and dale or various other predetermined runs/walks. Typical treadmills, however, are not capable of speed changes without physical input by the operator. Those that are capable of instantaneous speed change contain unduly complex mechanisms. A user needs virtually instant speed changes to adapt the treadmill speed to conditions under which the runner/walker is either ahead or behind the pace set on the treadmill. Such speed change capabilities are not only useful but also serve as a safety net to prevent a user from colliding with the control panel or falling off of the back of the treadmill, neither an unusual occurrence. It is seldom convenient for a user to have to press or change controls to adjust speed of the treadmill. Automatic speed adjustment is therefore of particular benefit in both convenience and safety. Automatic speed control is not new to the art. The methods of automatically controlling speed, though, vary significantly. The current invention offers a unique approach to speed control.